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Influence of Mineral Composition of Melaphyre Grits on Durability of Motorway Surface

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Influence of Mineral Composition of Melaphyre Grits on Durability of Motorway Surface Physicochemical Problems of Mineral Processing, 38 (2004) 341-350 Fizykochemiczne Problemy Mineralurgii, 38 (2004) 341-350 Tadeusz CHRZAN4 INFLUENCE OF MINERAL COMPOSITION OF MELAPHYRE GRITS ON DURABILITY OF MOTORWAY SURFACE Received April 4, 2004; reviewed; accepted June 5; 2004 The surface layer of the Konin-Września motorway section was made between July and November of 2001. Although the tests of melaphyre aggregates against grade and class requirements had confirmed that grits were the first class and grade according to the Polish standards, the motorway has been wearing rapidly with the first repairs being carried out as early as 2003. The motorway surface has been excessively worn and looks as if it were used for at least 5 years. The paper explains why the motorway surface has been worn so rapidly. Key words: motorway, ,melaphyre grit, weathering INTRODUCTION The surface layer of the Konin-Września motorway section was made during the period from July to November 2001. The layer was made with granulated aggregate 0- 20 mm in diameter from Borówko and Grzędy melaphyre quarry, bounded with modified bituminous mass. The tests of melaphyre aggregates against grade and class requirements had confirmed that the grits were the first class and grade (Chrzan, 1997; Wysokowski, 2000/2001) according to the Polish Standards (PN-11112:96, PN- 11110:96, PN-EN 1097-2). The binding layer of asphaltic concrete made and tested on samples that were taken from the completed motorway also conformed to the standard requirements according to Polish Standards (PN-S/96025, PN-74/S-96022). Also, the adhesion of asphalt to the melaphyre grit conformed to the standard (PN-84/B-6714/22). After the wintertime, in spring 2002, on the surface of the roadway, distinct signs of scaling and weathering were observed on the surface of larger melaphyre grit grains. In August 2002, it was found that the number of weathered grains had 4 Institute of Environmental Engineering, University of Zielona Góra, Poland 342 T. Chrzan increased and some of them lost their compactness and disintegrated (Ruttmar, 2002). Between September and November of 2003, due to the above reason, which threatened the safety of moving vehicles, partial repairs were carried out covering 1600 square metres. The surface of motorway has been excessively worn and looks as if it were used for at least 5 years. In this paper, it is explained why the motorway has been worn so quickly. ANALYSIS OF DECREASE OF ASPHALTIC CONCRETE STRENGTH OF MOTORWAY A2 BINDING LAYER IN RESPECT TO MINERAL COMPOSITION OF ROCKS DESCRIPTION OF MELAPHYRE DEPOSIT (Radziszewska-Jargosz, 1982; Szuszkiewicz I Król, 1988) The melaphyre used for road construction come from deposit that was formed from basalt-type volcanic rocks in the Permian period around 350 mln million years ago. The volcanic rocks created trachyte-basalt, trachyte and tuff-type rocks. The melaphyre deposit is exploited in the quarries of Borówno, Grzędy and Rybnica Leśna. The trachyte basalts are of two types. The first one includes rocks coloured cherry-brown, cherry-brick and grey-violet. They have chaotic structure and aphanitic texture. Cracks are filled with the ferruginous and carbonate substance. The second type is the rock ranging from grey-brown through grey-greenish to nearly black in colour. The structure is aphanitic and the texture is dense. Course- grained breccia of chaotic texture is also found. Volcanic spalls are cemented with the ferruginous and carbonate binder. The rock spalls are grey-brown and are of various size and aphanitic structure. The tuffs are cherry-brown, have aphanitic structure and chaotic, texture. They disintegrate into irregular small blocks. Numerous quartz grains and carbonate veins are visible. The sedimentary rocks are cherry-brown in colour and have fine-grained structure with directional texture. They disintegrate into irregular small blocks. Rocks of lava- mudstone fraction are found in the deposit which may have been the result of lava flooding during volcano eruption of weathered layers from the previous outflow. The exploited rock is melaphyre-type aphanite lava ranging from dark grey to black in colour; solid but intensely cracked rock. The cracks make it vulnerable to weathering and 0-10 mm sized rock is dumped as waste (Kancler, 2002a) in amount of 21% at Borówno quarry, and 15% at Grzędy quarry (Kancler, 2002b). This gives evidence that malaphyre in the Borówno quarry is built from minerals that are subject of stronger weathering than that in the Grzędy quarry. The melaphyre (Kancler, 2002a and 200b) in both quarries is built from minerals that disintegrate under the influence of temperature, air and water. Influence of mineral composition of melaphyre grits on durability of motorway surface 343 PETROGRAPHIC ANALYSIS OF MELAPHYRE The petrographic analysis of Grzędy deposit (Radziszewska-Jargosz, 1982) shows that plagioclases are found in the form of small phenocrysts. Feldspars undergo the process of sericitization and carbonization, and weathering processes lead to kaolinization. The ferruginous substance infiltrates the strips of plagioclases. Dark minerals were completely transformed. They were replaced with hydrated iron oxides accompanied by concentrations of carbonates, and in place of olivine there is a substance that is difficult to identify. Chlorite is rarely found. Pores are refilled with calcite accompanied by ferruginous pigment. In the pores there are concentrations of chalcedony. Concentrations of limonite are often found. Apatite, ilmenite and magnetite are accessory minerals. Volcanic glass, brown or orange in colour is also found. The rock groundmass consists of heavily carbonatizated glass, perches of plagioclases, ash fraction and iron oxides. PROPERTIES OF MINERALS FOUND IN THE MELAPHYRE DEPOSIT [Bolewski I Manecki, 1993; Bolewski, 1972; Chrzan, 1997) On the basis of geological documentation [8] on melaphyre deposit of the Borówno quarry, the mineralogical composition of fresh samples collected from the deposit is as follows: plagioclase 45.2-75.0 %, pyroxene 0-5.81 %, oxides and hydroxides 6.1-38.7 %, carbonates 0-8.3 %, chlorite 0-4.7 %, clayey minerals 0-5.2 %, quartz 0-3.0 %, iddingsite 0-9.7%, and unidentified 0-1.0 %. Feldspars (plagioclases) Plagioclases are sodium-calcium (Ca, Na) feldspars. Also found, there are potassium (K), white (Na) and lime (Ca) feldspars. The feldspars, more generally called aluminosilicates, form mixed crystals where K, Na, and Ca combined in different proportions among themselves and silica. Specific density of feldspars ranges from 2.5-2.8 Mg/m3. With an increase of calcium (Ca) content, plagioclases disintegrate easier into clay minerals, in particular into kaolinite. The kaolinization of plagioclases is commonly known among geologists. The weathering product of plagioclases that are rich in calcium is also calcite (CaCO3) coloured yellowish or brown. Kaolinite is the basic component of clayey minerals coloured red or brown and with specific density 2.5-2.6 Mg/m3, which is found in the form of dense or scaly concentrations. Wet kaolinite becomes plastic. The clayey minerals also include montmorillonite with specific density 2.0 Mg/m3 and in the form of white dense or scaly concentrations, which intensely swells in water, and decolourises denatured alcohol or methylene blue solution. Bentonite of the same colour and density behaves in a similar way; it is a mixture of clay minerals of the montmorillonite group. Feldspars also undergo the processes of sericitization and carbonisation. From the potassium feldspars, sericite is formed of scaly structure, and chlorite of scaly structure. 344 T. Chrzan Micas, such as muscovite, are found in the form of lamellas or lamella concentrations. These are minerals, formed of Na, K, Al, Fe, Mg, Si elements in various combinations. Mica is found in the magma rocks rich in SiO2 such as granites. In sedimentary rocks, it transforms into hydro-muscovite. They are green and black, yellow or brown in colour. Sericite has the form of tiny scales and is created at low hydrothermal temperatures. Sericitization takes place when feldspar turns to sericite. Pyroxenes Pyroxenes belong to aliphatic silicates and aluminosilicates. Group 1 consists of Mg-Fe, Mn-Mg, Ca, Ca-Na, Na-type pyroxenes. Pyroxenes is an important group of rock-forming minerals, which are created at high temperatures and at low water pressure. They are components of magma rocks and metamorphic rocks. They are not resistive to climatic factors, therefore are rarely found in sedimentary rocks. The colour of pyroxenes depends on iron and titanium content. At small content, it ranges from white to greenish, with larger content, it is olive, brown or dark green. Orthorhombic pyroxenes form the isomorphous series from Mg to Fe, with distinguished enstatite, bronzite, hypersthene, ferrohyperstene, eulite. Monoclinic pyroxenes include four minerals creating a diopsyde-hedenbergite series built from Ca, Mg, Fe, SiO2. Iron oxides and hydroxides Hematite (Fe2O3) has a cherry colour in variety of shades. It is insoluble. It may instantly oxidize in weak acids. In small quantities, it is found in magma rocks, especially those coloured red. It is a component of hydrothermal formations. Geothyte (FeOOH) ranges from brown to is red in colour. It is a product of hydrothermal activity at low temperature. It often occurs as an admixture colouring other rocks and in melaphyre vacuum. It is a product of iron mineral oxidation. Carbonates Calcite (CaCO3) is ranging from white to brown in colour. A component of sedimentary rocks, such as limestone, chalk, marls. It is formed in the hydrothermal activity zone independently fills rock crevices. Aragonite (CaCO3) is from white to brown in colour and is found in granular or dripstone crevices of melaphyres and basalts. It is a mineral of hydrothermal zone. Dolomite (CaMg(CO3)2) is a sedimentary rock mineral ranging from white to black in colour with density 2.8-2.9 Mg/m3 and is found in granular or dense form.
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